Persist global app settings and expose startup/auto-connect controls. Adds AppSettings (StartWithWindows, AutoConnectOnStartup, LastActiveProfileId) plus LoadAppSettings/SaveAppSettings to ProfileService (appsettings.json). MainViewModel now loads/saves these settings, exposes StartWithWindows/AutoConnectOnStartup/LastActiveProfileId properties, restores last profile and triggers auto-connect on startup when enabled, and updates the HKCU Run registry entry to enable/disable startup (with a user warning message on enable). Adds corresponding UI controls to SettingsTabView and includes defensive error handling and sensible defaults.
MaxiFan